1. Field
The exemplary embodiments disclosed herein relate to three-dimensional (3D) cameras including a wavelength-variable light source and methods of measuring transmittance using the same.
2. Description of the Related Art
In addition to a general function of photographing images, a 3D camera has a function of measuring distances from a plurality of dots on an object surface to the 3D camera. Various algorithms for measuring a distance between an object and a 3D camera, such as a time-of-flight (TOF) method, have been used. In the TOF method, a flight time of an illumination light emitted toward an object, reflected from the object, and received at a light receiving unit is measured. The flight time of the illumination light may be obtained by measuring a phase delay of the illumination light, i.e., a phase difference between light emitted to a subject and light reflected from the subject. A high-speed optical modulator may be used to accurately measure the phase delay.
A transmission type shutter having superior electricity-optical response characteristics has been used in order to obtain a 3D image with high distance precision. Recently, a transmission type shutter having a PIN diode structure has been used. The transmission type shutter is used to correct an effect of temperature on transmittance since a transmittance spectrum may vary with temperature as well as an applied voltage. Recently, a method of estimating a transmittance spectrum by measuring the internal temperature of a 3D camera, which is an indirect method, has been used as a transmittance correction method. However, according to the above method, it is impossible to directly measure the internal temperature of a transmission type shutter and errors may occur while estimating transmittance via the internal temperature.